en carrier, and in a runt
(_pigeon cygne_), was longer by above the tenth of an inch than would
follow from the length of the beak proportionally with that of the
rock-pigeon. In one carrier the orifice of the nostrils was thrice as long
as in the rock-pigeon, though in body and length of beak this bird was not
nearly double the size of the {169} rock-pigeon. This greatly increased
length of the orifice of the nostrils seems to stand partly in correlation
with the enlargement of the wattled skin on the upper mandible and over the
nostrils; and this is a character which is selected by fanciers. So again,
the broad, naked, and wattled skin round the eyes of carriers and barbs is
a selected character; and in obvious correlation with this, the eyelids,
measured longitudinally, are proportionally more than double the length of
those of the rock-pigeon.

The great difference (see woodcut No. 27) in the curvature of the lower jaw
in the rock-pigeon, the tumbler, and Bagadotten carrier, stands in obvious
relation to the curvature of the upper jaw, and more especially to the
angle formed by the maxillo-jugal arch with the premaxillary bones. But in
carriers, runts, and barbs the singular reflexion of the upper margin of
the middle part of the lower jaw (see woodcut No. 25) is not strictly
correlated with the width or divergence (as may be clearly seen in woodcut
No. 26) of the premaxillary bones, but with the breadth of the horny and
soft parts of the upper mandible, which are always overlapped by the edges
of the lower mandible.

In pouters, the elongation of the body is a selected character, and the
ribs, as we have seen, have generally become very broad, with the seventh
pair furnished with processes; the sacral and caudal vertebrae have been
augmented in number; the sternum has likewise increased in length (but not
in the depth of the crest) by .4 of an inch more than would follow from the
greater bulk of the body in comparison with that of the rock-pigeon. In
fantails, the length and number of the caudal vertebrae have increased.
Hence, during the gradual progress of variation and selection, the internal
bony frame-work and the external shape of the body have been, to a certain
extent, modified in a correlated manner.

Although the wings and tail often vary in length independently of each
other, it is scarcely possible to doubt that they generally tend to become
elongated or shortened in correlation. This is well seen in j